sfranchi, tell me/us about your dough handling process. Blisters/bubbles is also a symptom of inadequate fermentation and/or cold dough going into the oven. I have found that if my dough is sufficiently mature, and I let it temper at room temp for 30 to 45 minutes before baking, then I get little to no bubbling whatsoever.
How are you handling your dough?